title: Enforced expression of miR-125b affects myelopoiesis by targeting multiple signaling pathways.
abstract: MicroRNAs (miRNAs) are small, noncoding RNAs that regulate gene expression by sequence-specific targeting of multiple mRNAs. Although lineage-, maturation-, and disease-specific miRNA expression has been described, miRNA-dependent phenotypes and miRNA-regulated signaling in hematopoietic cells are largely unknown. Combining functional genomics, biochemical analysis, and unbiased and hypothesis-driven miRNA target prediction, we show that lentivirally over-expressed miR-125b blocks G-CSF-induced granulocytic differentiation and enables G-CSF-dependent proliferation of murine 32D cells. In primary lineage-negative cells, miR-125b over-expression enhances colony-formation in vitro and promotes myelopoiesis in mouse bone marrow chimeras. We identified Stat3 and confirmed Bak1 as miR-125b target genes with approximately 30% and 50% reduction in protein expression, respectively. However, gene-specific RNAi reveals that this reduction, alone and in combination, is not sufficient to block G-CSF-dependent differentiation. STAT3 protein expression, DNA-binding, and transcriptional activity but not induction of tyrosine-phosphorylation and nuclear translocation are reduced upon enforced miR-125b expression, indicating miR-125b-mediated reduction of one or more STAT3 cofactors. Indeed, we identified c-Jun and Jund as potential miR-125b targets and demonstrated reduced protein expression in 32D/miR-125b cells. Interestingly, gene-specific silencing of JUND but not c-JUN partially mimics the miR-125b over-expression phenotype. These data demonstrate coordinated regulation of several signaling pathways by miR-125b linked to distinct phenotypes in myeloid cells.
authors.affiliation: Department of Hematology, Hemostasis, Oncology and Stem Cell Transplantation, Hannover Medical School, Hannover, Germany.
authors.forename: Ewa
authors.initials: E
authors.lastname: Surdziel
authors.forename: Maciej
authors.initials: M
authors.lastname: Cabanski
authors.forename: Iris
authors.initials: I
authors.lastname: Dallmann
authors.forename: Marcin
authors.initials: M
authors.lastname: Lyszkiewicz
authors.forename: Andreas
authors.initials: A
authors.lastname: Krueger
authors.forename: Arnold
authors.initials: A
authors.lastname: Ganser
authors.forename: Michaela
authors.initials: M
authors.lastname: Scherr
authors.forename: Matthias
authors.initials: M
authors.lastname: Eder
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology / Q000378:metabolism; D016923:Cell Death; D002454:Cell Differentiation; D002460:Cell Line; D049109:Cell Proliferation; D004247:DNA / Q000378:metabolism; D015870:Gene Expression; D016179:Granulocyte Colony-Stimulating Factor / Q000378:metabolism*; D006098:Granulocytes / Q000166:cytology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D035683:MicroRNAs / Q000235:genetics*; D022423:Myeloid Cells / Q000166:cytology / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D015854:Up-Regulation; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000235:genetics / Q000378:metabolism
chemical_list: C494773:Bak1 protein, mouse; D035683:MicroRNAs; C527468:Mirn125 microRNA, mouse; D050796:STAT3 Transcription Factor; C494087:Stat3 protein, mouse; D050998:bcl-2 Homologous Antagonist-Killer Protein; D016179:Granulocyte Colony-Stimulating Factor; D004247:DNA